Theta vacuum effects on QCD phase diagram

TL;DR

This paper investigates how theta vacuum effects influence the QCD phase diagram, revealing that increasing theta strengthens the chiral transition and can induce a first-order transition at zero chemical potential.

Contribution

It introduces a study of theta vacuum effects on the QCD phase structure using the PNJL model, highlighting the impact of theta on the nature of the chiral transition.

Findings

Chiral transition becomes stronger with increasing theta.

For large theta, the transition becomes first order at zero chemical potential.

Theta vacuum effects significantly alter the QCD phase diagram.

Abstract

Theta vacuum effects on the QCD phase structure in the \mu-T plane are studied by using the Polyakov-loop extended Nambu-Jona-Lasinio model and its extension, where \mu is the quark chemical potential and T is temperature, respectively. As the parameter \theta of the theta vacuum increases, the chiral transition becomes stronger. For large \theta, it eventually becomes first order even at zero \mu.